The effect of CART on pituitary hormones release from cultured pituitary cells harvested from fasted and fed ad libitum male rats.

Cocaine and Amphetamine-Regulated Transcript (CART) is widely expressed in the central nervous system and in several endocrine organs. CART is an important factor in the regulation of energy homeostasis. The aim of the study was to assess the role of CART in physiological response of pituitary cells in a course of starvation. The pituitary cells harvested from starved and fed ad libitum male rats were cultured for 48h and treated with: 0.1nM, 1nM, 10nM or 100nM doses of CART. The medium was collected after 60min and stored at -70°C until samples were further assayed for: LH, FSH, PRL, GH, TSH and ACTH. We revealed that in cultures of pituitary cells collected from fasted rats the basal levels of the examined hormones were reduced. Incubation of pituitary cells of non-starved rats with any dose of CART reduced the concentration of LH and TSH, while the levels of the other hormones were decreased after administration only specific doses of CART. In cells of fasted rats no change in the concentration of gonadotrophins was observed. The PRL level was increased only in the 1nM dose of CART, while the 10nM and 100nM CART doses markedly enhanced GH and TSH. Moreover, administration of 1nM, 10nM and 100nM of CART to cultured cells of fasted rats resulted in a significant rise of the ACTH. Our results indicate that CART can directly affect the physiological release of PRL, ACTH, TSH and GH in pituitary cells of starved animals. Moreover, CART did not alter the LH and FSH suppression level, which is correlated with food deprivation. This data stays in contrast with the already proposed role of CART as an anorexigenic hypothalamic factor.

Nanoscale conductive pattern of the homoepitaxial AlGaN/GaN transistor.

The gallium nitride (GaN)-based buffer/barrier mode of growth and morphology, the transistor electrical response (25-310 °C) and the nanoscale pattern of a homoepitaxial AlGaN/GaN high electron mobility transistor (HEMT) have been investigated at the micro and nanoscale. The low channel sheet resistance and the enhanced heat dissipation allow a highly conductive HEMT transistor (Ids > 1 A mm(-1)) to be defined (0.5 A mm(-1) at 300 °C). The vertical breakdown voltage has been determined to be ∼850 V with the vertical drain-bulk (or gate-bulk) current following the hopping mechanism, with an activation energy of 350 meV. The conductive atomic force microscopy nanoscale current pattern does not unequivocally follow the molecular beam epitaxy AlGaN/GaN morphology but it suggests that the FS-GaN substrate presents a series of preferential conductive spots (conductive patches). Both the estimated patches density and the apparent random distribution appear to correlate with the edge-pit dislocations observed via cathodoluminescence. The sub-surface edge-pit dislocations originating in the FS-GaN substrate result in barrier height inhomogeneity within the HEMT Schottky gate producing a subthreshold current.

Effect of orexin A on the release of GnRH-stimulated gonadotrophins from cultured pituitary cells of immature and mature female rats.

Orexin A (OxA), also known as hypocretin 1, is a regulatory neuropeptide involved in the control of various autonomic and neuroendocrine functions. It appears to have a significant impact on the regulation of trophic hormones secretion by influencing the hypothalamus and the pituitary. Orexin A acts through two types of receptor found in the pituitary. This suggests the possibility of direct action of OxA at the adenohypophysis level. The aim of this study was to investigate the direct effect of OxA on GnRH (gonadotrophin-releasing hormone)-stimulated LH and FSH secretion from cultured pituitary cells of sexually immature and mature female rats. Anterior pituitary cells obtained from immature and mature female rats (ovariectomized, and ovariectomized and treated with estradiol) were incubated with 10(-10)M or 10(-7)M orexin A for 1 hour and 4h and the effect on GnRH-stimulated (10(-9)M or 10(-6)M) LH and FSH release was examined. The concentrations of secreted gonadotrophins in the culture media were determined by RIA methods. Orexin A significantly inhibited GnRH-stimulated FSH release from pituitary cells isolated from immature female rats, whereas in cells of mature ovariectomized animals, the effect of OxA was dependent on the stimulatory dose of GnRH. When the cells were stimulated with a low dose of GnRH, orexin A inhibited the secretion of gonadotrophins, but when a high dose of GnRH was used, orexin A increased mainly the release of LH. In cultured pituitary cells from ovariectomized, estrogenized mature rats, orexin A inhibited the secretion of LH if the cells were stimulated with a high dose of GnRH. In conclusion, the results of this study revealed that orexin A may modify the sensitivity of gonadotrophic cells to GnRH, and its effect depends on the maturity and estrogen status of the rats from which the cells are isolated.

Cortistatin and pituitary hormone secretion in rat.

Cortistatin (CST), a novel neuropeptide, shows high structural homology and functional resemblance with somatostatin. CST binds with high affinity to all somatostatin receptors, and contrary to somatostatin, is also able to bind with MrgX2 and GH secretagogue receptor of ghrelin (GHS-R1) receptors. The aim of the present investigation was to evaluate in vivo the effect of peripheral administration of cortistatin on pituitary hormone release in comparison with somatostatin (SS) treatment. Adult male rats used in the experiment, were given peripheral injection of cortistatin, somatostatin or vehicle. Blood was withdrawn 60 and 120 minutes thereafter. We found short lasting significant decrease of GH concentration as a result of administration of CST and SS when compared with saline injected controls. Prolactin levels were increased 60 min after cortistatin but not to somatostatin injection. There was no effect of CST on both LH and FSH concentration; however, SS administration influenced gonadotropin secretion. We conclude that cortistatin play a regulatory role in pituitary secretion. Moreover, some differences have been found when compared cortistatin to somatostatin. Thus, when analyzing the mechanism of cortistatin activity it is worth to consider the effect of binding with receptors of somatostatin, specific receptor for CST (MrgX2) and GHS-R.

Structural analyses of Nd-doped CeO thin films deposited by pulsed laser deposition.

CeO(2) thin films doped with neodymium oxides for application to gas sensors have been elaborated by the pulsed laser deposition technique. The films were deposited on orientated Si (100) substrates with variable deposition times (t = 90, 180 and 360 s) and molar fractions of Nd(2)O(3) (0, 6.5, 15, 21.5 and 27 at.%). The resulting Nd-CeO(2) thin films were characterized by means of X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy equipped with EDS (Energy Dispersive Spectrometer) microanalysis. From X-ray diffraction analyses, it is clearly established that the texture is modified by Nd additions. The preferred (111) orientations of the CeO(2) crystals change into the (200) orientation. The morphology of the CeO(2) grains changes from triangles, for pure CeO(2) thin films, to spherical grains for Nd-doped films. In addition, cell parameter analyses from X-ray diffraction data show that a partial chemical substitution of Ce by Nd should occur in the face-centred cubic lattice of ceria: this should give rise to Ce(1-x)Nd(x)O(2-z) phases with oxygen non-stoichiometry.

Neuroendocrine control of metabolic homeostasis in Polish centenarians.

Neuropeptides play a pivotal role in the control of metabolic homeostasis. We aimed to evaluate the release of neuropeptides involved in the control of energy homeostasis in relation to metabolic status in aging humans. The study group consisted of 183 women: 75 centenarians (above 100 yrs old), 26 elderly women (below 70 yrs), 45 younger women (mean 26 yrs) and 37 obese women (mean 41.6 yrs). Fasting plasma concentration of leptin, adiponectin, ghrelin active, neuropeptide Y (NPY) and insulin were measured. Our results showed several differences in the metabolic and neurohormonal status in the centenarian group. The incidence of hypertension, glucose intolerance, insulin resistance and dyslipidemia was lower compared with obese women. Leptin and NPY concentrations were significantly lower than in elderly and obese subjects. Moreover, NPY level was higher than that in the younger group. Plasma adiponectin values were higher than in any of the other group. Insulin levels were significantly lower compared with the young and obese groups. Furthermore, a negative correlation was found between adiponectin and HOMA-IR, and adiponectin and insulin. Ghrelin active concentrations were significantly lower compared with the young subjects. However, ghrelin levels were higher than in obese subjects. We conclude that altered neuropeptide activity in centenarians may play a role in the mechanisms contributing to prolonged survival.

The relationship between neuropeptides and hormones in starvation.

OBJECTIVES: Some hormonal disturbances were demonstrated in starvation. Leptin, NPY and galanin play an important role in the control of appetite and in the mechanism of hormone release. METHODS: In order to evaluate the effect of starvation on the relationship between leptin, neuropeptide Y (NPY) galanin and pituitary and gonadal hormones release, plasma leptin, NPY and galanin as well as serum LH, FSH, prolactin (PRL), estradiol, progesterone levels in non-starved female rats (in diestrus) and after 72 hrs of starvation were measured with RIA methods. Effects of leptin, NPY and galanin administration on pituitary and gonadal hormones were investigated in vivo and in vitro experiments. RESULTS: Plasma leptin, NPY and galanin as well as serum estradiol and progesterone concentrations were significantly lower in starved rats as compared with non-starved rats. However serum prolactin level was significantly higher in starved rats. Opposite effects after leptin and NPY administration on hormone release in vivo and in vitro experiments were observed in non-starved rats. However, in starved rats we did not find changes in pituitary and gonadal hormones release after leptin, NPY and galanin injection or the hormonal response was blunted. CONCLUSIONS: 1) The disturbances in neuropeptides activity and in hormones release were observed in starvation. 2) Leptin, NPY and galanin have direct and indirect effects on pituitary and gonadal hormones release. 3) In starvation the hormonal response to leptin, NPY and galanin is impaired.

Plasma leptin, neuropeptide Y (NPY) and galanin concentrations in bulimia nervosa and in anorexia nervosa.

OBJECTIVES: It has been reported that leptin and neuropeptide Y (NPY) play a role in the control of appetite and in the regulation of hormonal secretion. METHODS: Plasma leptin, neuropeptide Y (NPY) and galanin concentrations were estimated in 13 women with bulimia nervosa (BN) 19 women with anorexia nervosa (AN) and in 19 healthy women of the control group (CG). RESULTS: Plasma leptin concentration in BN was significantly higher than that in AN and it was lower as compared with the control group, despite the same BMI (body mass index) in both the groups. Plasma leptin level in AN was significantly lower as compared with the controls. Plasma galanin concentrations in AN and BN did not differ significantly from the control group. Plasma NPY concentration in AN was lower than that in the control group. However, plasma NPY level in BN was significantly higher as compared with AN and with the control group (CG). The observed increase of NPY in BN was independent of BMI because BMI in bulimia nervosa was normal. CONCLUSIONS: The data may suggest that other factors than body weight changes may be involved in the modulation of leptin and NPY release in BN. The pathological behaviour of patients with bulimia nervosa may result from disturbed NPY release which is the strongest orexigenic factor.

Does leptin modulate immune and endocrine response in the time of LPS-induced acute inflammation?

OBJECTIVES: In many studies it has been reported, that leptin may play an important role not only in the regulation of food intake and body weight but can modify immune response. The aim of our study was to estimate the effects of the administration of exogenous leptin on serum concentration of proinflammatory cytokines (interleukin 6-IL 6 and tumor necrosis factor alpha-TNF alpha) and anti-inflammatory cytokine (interleukin 10 - IL 10) during LPS induced acute inflammation. We also estimated leptin's influence on pituitary, thyroid, adrenal and gonadal hormones in response to lipopolysaccharide (LPS) induced acute inflammation. METHODS: Male rats Wistar-Kyoto were divided into four groups, which received respectively: placebo (0.9% NaCl), LPS, leptin and leptin with LPS. The TNF alpha and IL 6 serum concentrations were measured after 2 hours and IL 10 after 4 hours. The pituitary, thyroid, adrenal and gonadal hormones serum concentrations were measured after 2 and 4 hours. Cytokine concentrations were estimated using ELISA tests and hormones concentrations using RIA tests. RESULTS: Leptin did not have an effect on both cytokine responses (proinflammatory and anti-inflammatory) in the time of LPS-induced acute inflammation. Leptin enhanced LPS-induced increasing of corticosterone secretion after 2 hours and decreased LPS-induced inhibition of testosterone secretion after 4 hours. CONCLUSIONS: Leptin can modulate hormone response during LPS-induced acute inflammation.